4a hair consists of tightly coiled curls that have the circumference of a crochet needle. Slightly prone to breakage, Type 4 hair can be fragile, highly porous, and can be very fine and wiry. No need to fret though, as type 4a coilies tend to hold more moisture in their strands than their 4b and 4c counterparts.
Type 4B: Instead of coiling or curling, you have hair that bends in sharp angles. They look quite a bit like the letter Z. The curl is tighter and far less defined, having the circumference of an ink-pen. ... The hair texture, which is tightly coiled like all Type 4s, ranges from super fine and soft to coarse and wiry.
4C textures are similar to 4B textures, but the tightly coiled strands are more fragile and have a very tight zig-zag pattern that is sometimes indiscernible to the eye. This hair type experiences the greatest amount of shrinkage.